PROJECT SUMMARY This Institutional Training Grant (T32) is a resubmission of a proposal from the Perelman School of Medicine (PSOM) at the University of Pennsylvania (Penn) and the Children's Hospital of Philadelphia (CHOP) to train MD and MD/PhD fellows pursuing careers doing bench research in microbiology, microbial immunology and the role of the microbiome in health and disease. This application combines the talent and resources available at two independent, but linked institutions, Penn and CHOP. We are requesting 3 slots annually to enroll one fellow each year for up to 3 years of support. Seventeen highly accomplished faculty members with active NIH grants are listed as mentors. Harvey Friedman, MD, from the Adult Infectious Disease Division will serve as Program Director (PD) and Joseph St. Geme, MD, Chairman of Pediatrics at CHOP will be the associate-PD. Nine faculty mentors are from the Departments of Medicine, 4 from the Department of Microbiology, 2 from the Department of Pediatrics, 1 from the Department of Dermatology, and 1 from the Wistar Institute. The mentors include 6 women; a member from an underrepresented minority group; 10 with MD or MD/PhD degrees and 7 with PhD degrees; 3 Assistant, 4 Associate and 10 Professors. The applicant pool will come primarily from the Adult and Pediatric Infectious Diseases postdoctoral training programs, but enrollment will be open to all divisions and departments at Penn and CHOP who have MD and MD/PhD postdoctoral fellows interested in pursuing bench research careers in microbiology, immunology and the human microbiome. Candidates interested in pursuing bench research careers in these disciplines are well represented among the fellowship trainees in the divisions and departments with mentors on this grant, which highlights the strengths of our applicant pool. Fellows interested in applying for a position on the T32 grant will generally apply during their first year of fellowship with the expectation that they will enter the grant in their second fellowship year. Fellows will apply by submitting their CVs, letters of reference from prior lab mentors and their fellowship director, and a record of their grades during undergraduate and postgraduate training. Each trainee selected for a position will have a scientific mentor (the lab PI) and a career mentor (a senior faculty member at Penn or CHOP). The Executive Committee will review the research progress of trainees semi-annually and an Advisory Committee comprised of two scientists from outside Penn and one from Penn will meet with trainees to review their progress annually. The environment and resources at Penn and CHOP for training in biomedical research are exceptional. The superb quality of the mentors, the outstanding credentials of the applicants and the dedication of the Executive Committee to ensure that every trainee receives the highest quality mentoring possible adds to our confidence that we will be addressing the urgent need to train the future physician scientist leaders in the disciplines of microbiology, microbial immunology, and microbiome research.